My car started doing that but only when under load ( towing caravan) then it got progressivly wprse would do it just if i put my foot down in 4 or 5th
had the codes read and it was injector bother . ford wanted £250 each injector and £200 to fit and re programme
So naturally i said bollox to that and hunted for then on the net and got a full set delivered to my door for £250 off ebay
Fitted them myself ( had to buy an injector tool £24)
then paid ford £92 to re programme them that was a year ago and its all hunky doory
My advise would be get your codes read as the glow plug light is the fault light and it could be any thing from an injector to a sensor failing